Heat exchanger

ABSTRACT

There is disclosed a heat exchanger comprising at least one set of channels having a proximal end and a distal end, the set of channels comprising: a first channel defined by a first skin and a wall; and a second channel defined by a second skin and the wall, wherein the wall located between the first channel and the second channel comprises a first at least one aperture to allow fluid to pass through the wall from the first channel to the second channel.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/603,481 filed Oct. 13, 2021, which is a national phase applicationfiled under 35 USC § 371 of PCT Application No. PCT/GB2020/051004 withan International filing date of Apr. 23, 2020, which claims priority ofGB Patent Application 1906005.2 filed Apr. 30, 2019 and EP PatentApplication 19275062.8 filed Apr. 30, 2019. Each of these applicationsis herein incorporated by reference in its entirety for all purposes.

FIELD OF THE DISCLOSURE

The present disclosure relates to a heat exchanger. In particular, thedisclosure is concerned with a heat exchanger for a land, sea or airvehicles subject to high temperatures or for a heat exchanger for astationary structure or equipment. In this application the term vehiclemay apply to any moving system (land, sea or air) and land based systemmay apply to a vehicle or a stationary structure/equipment.

BACKGROUND

Vehicles and land-based systems may generate and be subject tosignificant amounts of heat in operation. Cooling systems have been usedto reduce the temperatures in parts of vehicles or land-based systems.These cooling systems may take the form of active systems, such as heatexchangers, or passive systems.

Heat exchangers are systems that are designed to transfer heat betweentwo different media. Typically, there is a heat exchanging medium in theheat exchanger for transferring the heat from one region to anotherregion. The heat exchanging medium may be solid or a fluid. Heatexchangers may be used for vehicles or land-based systems to provideactive cooling to structure and/or equipment or remove heat from heatsensitive equipment.

There is a need to create an improved “active” skin cooling system foruse with vehicles and land-based systems that generate and be subject tosignificant amounts of heat in operation.

SUMMARY

According to a first aspect, there is provided a heat exchangercomprising at least one set of channels having a proximal end and adistal end, the set of channels comprising: a first channel defined by afirst skin and a wall; and a second channel defined by a second skin andthe wall, wherein the wall located between the first channel and thesecond channel comprises a first at least one aperture to allow fluid topass through the wall from the first channel to the second channel.

In one example, the heat exchanger comprises an inlet port for receivingsaid fluid and an outlet port for allowing the fluid to exit the heatexchanger.

In one example, the inlet port is coupled to the first channel and theoutlet port is coupled to the second channel.

The inlet port and the outlet port may be arranged at the proximal endof the set of channels. In other examples the inlet port is arranged atthe proximal end of the set of channels and the outlet port is arrangedat the distal end of the set of channels.

In one example, the set of channels comprises a third channel defined bythe first skin and the wall, wherein the wall located between the secondchannel and the third channel comprises a second at least one apertureto allow fluid to pass through the wall from the second channel to thethird channel.

The inlet port may be connected to the first channel at the proximal endof the set of channels and the outlet port may be connected to the thirdchannel at the distal end of the set of channels. The second at leastone aperture may be located towards the proximal end of the set ofchannels. The first at least one aperture may be towards the distal endof the set of channels.

The set of channels may follow a non-linear path between the proximalend and the distal end. The first channel and the second channel may beparallel curves relative to each other. The non-linear path may besubstantially sinusoidal. The wall may be bonded to the first skin andthe second skin. The wall may be corrugated and comprise a firstlongitudinal section bonded to the first skin, a second longitudinalsection bonded to the second skin and at least one an inclined sectionbetween the first longitudinal section and the second longitudinalsection. The inclined section may be inclined at an angle ofapproximately 30 to 60 degrees relative to the first longitudinalsection and the second longitudinal section. The wall may have athickness of between 0.5 mm and 6 mm. The first skin and the second skinmay be formed of a titanium alloy. The heat exchanger may comprise aplurality of sets of channels.

According to another aspect of the invention, there is provided a methodof manufacturing a heat exchanger, wherein the heat exchanger ismanufactured using diffusion bonding and superplastic forming.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present disclosure will now be described with referenceto the accompanying drawings, in which:

FIG. 1 shows an example of a plan view of a cross section of a heatexchanger;

FIG. 2 shows a cross sectional view of the heat exchanger along Sectionlines A-A shown in FIG. 1;

FIG. 3 shows a portion of a cross-section of a wall having a warrengirder or corrugated profile;

FIG. 4 shows an example of a portion of a wall between a first skin andsecond skin;

FIG. 5 shows a section through a heat exchanger showing one or moreapertures in the wall;

FIG. 6 shows an example of an elevation B-B as indicated by markers B-Bin FIG. 1;

FIGS. 7A and 7B shows an example of fluid paths through a section of theheat exchanger;

FIG. 8 shows an example of the a section of the heat exchanger; and

FIG. 9 shows an example of the relationship between heat transfer andmass flow rate.

It will be appreciated that relative terms such as top and bottom, upperand lower, and so on, are used merely for ease of reference to theFigures, and these terms are not limiting as such, and any two differingdirections or positions and so on may be implemented.

DETAILED DESCRIPTION

FIG. 1 shows an illustrative example of a plan view of a heat exchanger100. In the example shown, the heat exchanger 100 comprises a set ofchannels 102. There are six sets of channels 102 shown in the example inFIG. 1, but in other examples, more or fewer than six sets of channels102 may be used. The set of channels 102 has a proximal end 104 and adistal end 106.

The set of channels 102 comprises a first channel 108 and a secondchannel 110. The first channel 108 and the second channel 110 arefluidly coupled to allow fluid to pass from the first channel 108 to thesecond channel 110.

The set of channels 102 are located between a first skin 116 and asecond skin 118 of the heat exchanger 100, which are shown in moredetail in FIG. 2.

In the example shown in FIG. 1, in addition to the plurality of sets ofchannels 102 comprising the first channel 108 and the second channel110, there are also two isolated channels 114 that do not receive fluid.The isolated channels 114 are exterior channels that may act as staticpressure vessels and are not subjected to fluid flow, in use. In thisexample, the two additional channels 114 are located towards the side ofthe heat exchanger 100 such that the set of channels 102 is locatedbetween the two additional channels 114.

In the example shown in FIG. 1, fluid may enter the heat exchanger 100via one or more inlet ports 112 and exit the heat exchanger 100 via oneor more outlet ports 113. In other examples, fluid may enter the heatexchanger via an opening the in first skin or the second skin.

FIG. 1 shows that there may be one or more wall sections 120 separatingthe first channel 108 and the second channel 110 of each set of channels102. The wall sections 120 between the first channel 108 and the secondchannel 110 of the set of channels 102 may comprise one or more holes orapertures 142 to enable fluid to pass from the first channel 108 to thesecond channel 110. The apertures are described in more detail inrelation to FIG. 5.

FIG. 2 shows a section view through the example of the heat exchanger100 in FIG. 1 as taken along section markers A-A in FIG. 1. FIG. 2 showsan example of the first skin 116 and the second skin 118 with the atleast one of pair of channels 102 located between the first skin 116 andthe second skin 118.

In some examples, the first skin 116 is a lower skin located above thefirst channel 108 and the second channel 110 and the second skin 118 isan upper skin located below the first channel 108 and the second channel110. The first skin 116 and the second skin 118 are shown as beingsubstantially planar in this example, but in other examples, the profileof the skin platen 116 and second skin 118 may not be planar and may beshaped so as to fit the shape of the apparatus that requires cooling.

In some examples, the wall 120 is a single continuous element thatextends across and defines a plurality of sets of channels 102. However,in the other examples, the wall 120 may comprise a plurality of discreteelements, with an element of the wall 120 located between adjacent firstchannels 108 and second channels 110.

The wall 120 may have a shaped profile so as to define the plurality offirst and second channels 108, 110, together with the first skin 116 andthe second skin 118, in the heat exchanger 100. In one example, the wall120 comprises a warren girder profile in cross-section, as shown indetail in FIGS. 2, 3 and 4.

FIG. 3 shows a portion of an example of a wall 120 having a warrengirder or corrugated profile in cross section. In this example, the wall120 is a continuous element comprising a plurality of longitudinalsections 122, 124 separated by a plurality of inclined sections or webs126, 128. In this example, the plurality of longitudinal sections 122,124 are arranged along two planes such that alternate longitudinalsections 122, 124 are arranged on different planes, i.e. a firstlongitudinal section 122 and a second longitudinal section 124 arearranged on different planes are connected by an inclined section 126,128. A first set of alternating longitudinal sections 122 are arrangedalong a first plane and a second set of alternating longitudinalsections 124 are arranged along a second plane. In one example, thefirst set of alternating longitudinal sections 122 are coupled to orbonded with the first skin 116 and the second set of alternatinglongitudinal sections 124 are coupled to or bonded with the second skin118.

The wall 120 may form a repeating pattern of first longitudinal sections122 and second longitudinal sections 124 connected by one or moreinclined webs 126, 128. In one example, the wall 120 is corrugated andthe at least one set of channels 102 are defined by a first platen 116,a second platen 118 and the corrugated wall 120.

FIG. 4 shows an example of a portion of the wall 120 between the firstskin 116 and the second skin 118. The first channel 108 is defined bythe wall 120 and the first skin 116 and the second channel 110 isdefined by the wall 120 and the second skin 118. A first set oflongitudinal sections 122 of the wall 120 are connected to or bondedwith the second skin 118 and a second set of longitudinal sections 124are connected to or bonded with the first platen 116. In some examples,the angle of the inclined section or web 126, 128 is approximately 45degrees relative to the longitudinal sections 122, 124 of the wall 120and first skin 116 or second skin 118. However, in other examples, theangle of the incline section 126, 128 may range from approximately 30degrees to approximately 60 degrees relative to the longitudinalsections 122, 124 of the wall 120 and first skin 116 or second skin 118.The geometry is applicable to DB/SPF manufacture as the angles result inmanageable levels of superplastic strain in the wall 120. A 30 degreeangle of the inclined section or web 126, 128 would nominally result inan SPF strain of 100% and a halving of original thickness in thehorizontal plane prior to forming.

Forming a heat exchanger from only three layers, in this case the firstskin 116, the second skin 118 and the wall 120, means that ultrasonictesting can be carried out on the heat exchanger 100 to check the heatexchanger has formed correctly. Further, ultrasonic testing can be usedto test for any structural irregularities during the life of the heatexchanger.

As shown in FIG. 4, as the first channel 108 is defined by a first skin116 and a wall 120; and the second channel 110 is defined by a secondskin 118 and the wall 120. For example, as shown in FIG. 4, the firstchannel 108 is defined by the longitudinal section 122 and the inclinedsections 126, 128 of the wall 120 and the first skin 116. Further, thesecond channel 110 is defined by the longitudinal section 124 and theinclined sections 126, 128 of the wall 120 and the second skin 118. As aresult of this example, fluid passing through the first channel 108 hasa large contact surface area with the first skin 116. As such, if thefirst skin 116 is subject to the hot side of the heat exchanger 100 thatrequires cooling, then more of the heat can be absorbed by the fluidpassing through the first channel 108. The fluid will then pass throughthe first at least one aperture 142 in the wall 120 separating the firstchannel 108 and the second channel 110. The second channel 110 has alarge contact surface area with the second skin 118. As a result, someof the heat may be transferred from the fluid to the second skin 118,which may be at a lower temperature compared with the first skin 116 butwith the intention that the cooling effect is high in channel 108 andthat the higher proportion of the heat transferred from the first skin116 will remain with the fluid as it then flows along the second channel110 and is not transferred excessively into the cooler skin 118 but isinstead transferred with the fluid as it exits the heat exchanger 100.In one example, the fluid that exits the heat exchanger 100 may passinto a secondary heat exchanging device (e.g. a radiator or similar).

In one example, the first skin 116 and the second skin 118 each have athickness of approximately 2 mm but in practice, any thickness may beconsidered depending on the application. The distance between the insideface of the first platen 116 and the inside face of the second platenmay be approximately 16 mm but could be perhaps as much as 100 mm. Thematerial thickness is designed to accommodate a pressure ofapproximately 20 bar. The wall 120 may have a thickness of between about0.5 mm and 6 mm depending on the application. For a ground-based coolingsystem where weight is not of consequence the wall 120 could be 6 mmthick. For an air vehicle a wall would more typically be between 0.5 mmand 2 mm. This web thickness therefore de-risked the manufacturingquality to add strength to the channels under working conditions.

In one example, the first channel 108 is suitable for receiving acoolant fluid via an inlet port 112. The second channel 110 may beconnected to an outlet port 113 for allowing the coolant fluid to leavethe second channel 110. In some examples, the inlet port 112 may beintegrated with the first channel 108 and the outlet port 113 may beintegrated with the second channel 110. In other examples the inlet port112 and the outlet port 113 may be plumbed using a pipe connector to thefirst channel 108 and the second channel 110.

In one example the inlet port 112 is substantially cylindrical. Theoutlet port 113 may be substantially cylindrical. The substantiallycylindrical inlet port 112 includes an inner diameter 132, defining ahole 134, and an outer diameter 136. In one example, the inlet port hasa hole 134 of approximately 8 mm and an outer diameter of approximately10 mm.

The inlet port 112 provides a method for allowing a coolant fluid totransit from a source of fluid to the heat exchanger 100. Due to thesignificant pressures in use in the heat exchanger 100, associatedpipework through which the coolant fluid is provided to the inlet port112 may be welded to the interface of the inlet port 112. To be able toweld the associated pipework to the inlet port 112, an area around thewelded location had to be created to accommodate the pipework, weld andassociated heat generated during this process. These criteria generatedthe cross-sectional area required to securely support and manage theheat load during assembly.

In one example, the at least one inlet port 112 and the at least oneoutlet port 113 are alternately arranged at the proximal end 104 of theat least one set of channels 102, such that an outlet port 113 isarranged in between two inlet ports 112.

In the example shown in FIG. 1, the inlet and outlet ports 112, 113 areconnected directly into the set of channels 102. However, in otherexamples, the inlet ports 112 and outlet ports 113 are connected throughthe first skin 116 and/or second skin 118.

In other examples, the set of channels 102 comprises a plurality ofchannels such that the fluid and the outlet port may be at either theproximal or distal end of the set of channels 102. Alternatively, theinlet or outlet ports 112, 113 may be arranged such that the fluid istransferred through the external platens or the ends of the channels.

FIG. 5 shows an example of one or more apertures 142 in the wall 120between the first channel 108 and the second channel 110 of the set ofchannels 102. In one example, the first channel 108 and the secondchannel 110 are fluidly coupled via the one or more apertures 142located in the wall 120 between the first channel 108 and the secondchannel 110. The one or more apertures 142 may be formed in the inclinedsection 128 of the wall 120. In FIG. 5, the apertures 142 are shown asbeing circular shaped, but other shapes are envisaged.

In some examples, the one or more apertures 142 are arranged towards thedistal end of the at least one set of channels 102. In one example,there are a plurality of apertures 142 spaced at between 10 mm and 20 mmalong the wall between the inlet channel and outlet channel, but othersizes are envisaged depending on the application of the heat exchanger.

The apertures may be of variable size depending on the required fluidtransfer rates and pressures. Specifically, in the case where there is aplurality of apertures the apertures may optimally be smaller towardsthe proximal end and progressively increase in size towards the distalso as to ensure that each aperture permits the desired share of thetotal flow to pass. In one example, the apertures will be made circularat the stage of manufacturing the wall 120 (or core sheet) in the DB/SPFprocess, but the effect of superplastic forming will then cause thecircular form to be uniaxially extended to an ellipse shape.Alternatively, an elliptical hole with the major axis transverse to thesuperplastic strain direction such that a circular final hole form willresult after forming. The thickness of the material at the locationwhere the gas transfer holes are introduced may also be of additionalthickness in order that the tendency for local thinning due tosuperplastic straining is counteracted.

One method of manufacturing the heat exchanger is using a DB/SPFprocess. The apertures 142 will be “gas transfer holes” introduced inthe core pack by simple hole drilling of the core sheet (which resultsin the wall 120 in the heat exchanger 100) at the detail manufacturingstage and before the application of stop-off compound to locally preventthe diffusion bonding of sheets so as to facilitate the subsequentformation of three dimensional structure by superplastic inflation ofthe core pack within an SPF tool cavity. There are various techniques tomanage the apertures 142 so as to avoid excessive elongation during SPF.In the example of the heat exchanger 100 being used with an air vehicle,avoiding excessive elongation could be important as the core sheet willbe as thin as possible for light weighting reasons. For ground-basedsystems the core thickness may be substantial and strain around theholes should not be excessive. The DB stage can cause the first platen116 to form into the hole in the core sheet, which forms the wall 120,and then seal the hole and potentially diffusion bond together (notingthat the area has a layer of stop-off applied).

The example of FIG. 5 also shows an example of a chamfer located at thedistal end of the heat exchanger 100. In one example, the chamfer isangled between 30 to 60 degrees, more particularly between 40 degreesand 50 degrees. The chamfer may result from the build orientation ofSelective Laser Melting manufacturing, which may be used to manufacturethe heat exchanger 100. The heat exchanger may be built in the verticaldirection upwards. The nature of this build orientation provides aself-supporting method of manufacture which is optimised at 45 degrees.

FIG. 6 shows an example of an elevation B-B as indicated by markers B-Bin FIG. 1. In this example, the inlet ports 112 and the outlet ports 113are arranged in an alternating nature at the proximal end 104 of the atleast one set of channels 102. For conciseness, not all of the inletports 112 and outlet ports 113 have been indicated with reference signs.Further, the centre line through the inlet ports 112 may be offset froma centre line of the outlet ports 113 by approximately 2 mm.

Referring to FIG. 1, there is shown a plan cross-sectional view of theheat exchanger 100. The arrows in FIG. 1 indicate the flow of fluid,such as coolant fluid, into the first channel 108, through the at leastone aperture 142 in the wall 120, and out of the second channel 110 viaan inlet port 112 and the outlet port 113 respectively. Note that forconciseness, not all inlet ports 112 and outlet ports 113 include arrowsindicating fluid flow. However, in practise, each of the inlet ports 112may receive a fluid flow and each of the outlet ports 113 may eject thefluid. In this example, the apertures 142 located towards the distal endof the set of channels 102, i.e. towards the opposite end of the set ofchannels 102 from the inlet port 112. In the example shown in FIG. 1,there are five apertures 142 shown in the wall 120 between the firstchannel 108 and the second channel 110. However, in other examples,there may be more or fewer than five apertures 142 between each wall 120separating the first channel 108 and the second channel 110 of the setof channels 102.

As can be seen in FIG. 1, each set of channels 102 is separated by asection of wall 120 that does not contain an aperture. Therefore, eachset of channels 102 is fluidly isolated from the other sets of channels102.

In one example, as fluid enters that heat exchanger 100 via the inletport 112, it travels along the first channel 108 from the proximal endof the set of channels 102 towards the distal end of the set of channelschannel 102. The apertures in the wall 120 between the first channel 108and the second channel 110 enable the fluid to pass through the wall 120comprising the apertures 142.

Once the fluid has passed to the second channel 110, it moves from thedistal end of the set of channels 102 to proximal end of the set ofchannels 102, i.e. the part of the second channel 110 that is adjacentto the outlet port 113. The fluid then exits the heat exchanger 100 viathe outlet port 113.

In one example a boundary wall 144 bounds the heat exchanger 100 suchthat as the fluid approaches the extreme distal end of the first channel108, any fluid that has not already passed through the one or moreapertures 142 will impinge upon the boundary wall 144 and then passthrough the one or more apertures 142, for example, the most distalaperture 142.

FIG. 7A shows an alternative example of a part of a heat exchanger 100.The heat exchanger 100 may have a different arrangement of apertures142, inlet ports 112 and outlet ports 113 such that the fluid may take adifferent path through the heat exchanger 100. For example, as shown inFIG. 7A, the fluid may enter the first channel 102 at the proximal end104 of the set of channels 102 and pass through a section of the firstchannel 108. The fluid may then pass through the at least one aperture142 in the wall 120 located between the first channel 108 and the secondchannel 110. In this example, the fluid will then continue insubstantially the same direction from the proximal end 104 to the distalend 106 of the set of channels 102 along the second channel 110 and exitthe second channel 110 at the distal end 106 of the set of channel 102.In this example, the fluid effectively travels from the proximal end 104to the distal end 106 of the set of channels 102 without turning back onitself. The inlet port 112 may be coupled with the first channel 102 atthe proximal end 104 of the set of channels 102 and the outlet port 113may be coupled with the second channel 110 of the set of channels 102 atthe distal end 106 of the set of channels 102.

FIG. 7B shows an alternative example of a part of the heat exchanger100. In this example, the set of channels 102 comprises a first channel108, a second channel 110 and a third channel 115. The third channel 115is defined by the first skin 116 and the wall 120. The wall 120 locatedbetween the second channel 110 and the third channel 115 comprises asecond at least one aperture 142 to allow fluid to pass through the wall120 from the second channel 110 to the third channel 115. The heatexchanger 100 may have a different arrangement of apertures 142, inletports 112 and outlet ports 113 such that the fluid may take a differentpath through the heat exchanger 100. For example, as shown in FIG. 7B,the fluid may enter the first channel 102 at the proximal end 104 of theset of channels 102 and pass through a section of the first channel 108.The fluid may then pass through the at least one aperture 142 in thewall 120 located between the first channel 108 and the second channel110. In one example, the at least one aperture 142 between the firstchannel 108 and the second channel 110 of the set of channels 102 islocated towards the distal end 106 of the set of channels 102. In thisexample, the fluid will then impinge on an end wall and travel along thesecond channel 110 from the distal end 106 to the proximal end 104 ofthe heat exchanger 100. The fluid may then pass through the one or moreapertures 142 located between the second channel 108 and a third channel115. In one example, the at least one aperture 142 located between thesecond channel 110 and the third channel 115 may be located toward theproximal end 104 of the set of channels 102. In this example, the fluidwill then travel from the proximal end 104 to the distal end 106 alongthe third channel 115 and exit through the heat exchanger 100 at anoutlet port 113.

In other examples, the set of channels 102 may include a fourth channel(not shown) and the fluid may pass through at least one aperture in awall located between the third channel 115 and the further channel andthen reverse in direction again. The fluid may travel to the other endof the heat exchanger and exit through an outlet port 113.

In one example, the fluid may follow a substantially linear path as itflows in the channels, i.e. the walls 120 of the channels are straight.However, in other examples, as shown in FIG. 1, the set of channels 102may follow a non-linear path, i.e. the first channels 108 are non-linearas they extends from right to left in FIG. 1 and the second channels 110are non-linear as they extend from left to right in FIG. 1. Thenon-linear path of the inlet channel 108 and the outlet channel 110introduces a turbulence to the fluid flow, which is required to follow anon-linear path through the first channel 108 and the second channel110. In other words, the set of channels 102 may have a non-linear path.

As shown in FIG. 1, the inlet channel 108 and the outlet channel 110 maycomprise parallel curves relative to each other. In other words, theinlet channel 108 and the outlet channel 110 are substantially the sameshape, but are translated relative to each other.

The manufacturing method of DB/SPF is capable of making non-linearchannels simply through the adoption of a stop-off pattern of suitablegeometry. Conversely, linear channels may also be formed.

As shown in FIG. 1, the fluid follows a substantially meandering path asit travels through the first channel 108 and the second channel 110. Inother words, the fluid may follow a non-linear path in the heatexchanger 100. FIG. 8 shows an example of the detail of the path of thefirst channel 108 and the second channel 110 in more detail. In theexample shown in FIG. 8, the first channels 108 and second channels 110follow a substantially sinusoidal path, defined by substantiallysinusoidal walls 120. In this example, the wall 120 is corrugated in afirst direction to form a plurality of sets of channels 102 andnon-linear in a second direction such that the plurality of sets ofchannels 102 are non-linear.

The non-linear or meandering path followed by the walls 120 (and hencethe set of channels 102) creates a turbulent fluid path for the coolantfluid to increase heat transfer of the heat exchanger 100. The turbulentfluid flow is more efficient for heat transfer compared with the laminarfluid flow because effectively, in laminar flow, fluid is moving indistinct streamlines. That means that the heat transfer is from one“layer” of the fluid to a cooler one, essentially by heat conduction. Incontrast, in turbulent flow the fluid particles are not moving alongstreamlines but are mixing from one layer to others, which means thatthere is physical transport of fluid from higher to lower temperaturesand vice versa, which significantly increases the heat transfer.

The non-linear or meandering path followed by the first channel 108 andthe second channel 110 increases the turbulence in the fluid flow bypreventing or reducing the formation of laminar layers of fluid. Assuch, the heat exchanger works 100 to effectively remove heat from aregion on one side of the heat exchanger 100, for example, from theregion adjacent the first skin 116 and transferred via the heatexchanger 100 to the region adjacent the second skin 118.

In one example, the coolant fluid used with the heat exchanger 100 isArgon. However, for a light-weight application, a liquid phase coolantwould run at a much lower operating pressure and so have less penalty interms of structural weight. In one example the liquid phase coolant isSyltherm 800 heat transfer fluid. The use of Syltherm 800 heat transferfluid enables the pressure in the heat exchanger to be substantiallyreduced.

In the example shown in FIG. 1, there are two additional channels 114located towards the edges or sides of the heat exchanger 100. Theseadditional channels 114 may or may not be associated with a port toenable a fluid to be received in the additional channels 114. Theseouter additional channels 114 may be the result of the manufacturingmethod, which requires additional space around the at least oneplurality of pairs of channels 102. These outer channels 114 do not forman active part of the heat exchanger 100.

In one example, the plurality of channels 102 are made from three sheetsof material formed into a tool cavity, i.e. the first skin 116, thesecond skin 118 and the wall 120. In one example, the first skin 116,the second skin 118 and the wall 120 is a titanium diffusion bondedtitanium alloy, such as Ti-6Al-4V, as this has excellent creepperformance at a desired operating temperature, for example 350 degreesCelsius, of the heat exchanger 100, allowing a high skin temperature. Atemperature of 350 degrees Celsius represents the region of stagnatedflow around leading edge aircraft skins for hypersonic flight, at theset test conditions. The titanium alloy material, therefore reducingload on cooling system solution. Further, Ti-6Al-4V retains its materialstrength under the high temperature conditions. In addition, Ti-6Al-4Vis also compatible with the Diffusion Bonding and Superplastic Formingmethod, which may be used for the manufacture of the heat exchanger 100.

DB/SPF (Diffusion Bonding and Superplastic Forming) is a process for theeconomic production of three-dimensional objects and sandwichstructures. One characteristic of DB/SPF is an extremely high level offormability. A separating agent or “stop-off”, such as yttria is placedon defined areas between material sheets, such as titanium alloys. Inthe example shown in FIG. 4, the stop-off 130 is applied to the sectionsof the first skin 116 and the second skin 118 at the flat-sheet detailsstage prior to assembly of the sheets for diffusion bonding. This thenresults in sections of the wall 120 being unbonded in the final product.In contrast, the areas of the first skin 116 and the second skin 118 inwhich the stop-off material 130 is not applied results in a diffusionbond between the wall 120 and the first skin 116 and the second skin 118in the finished product 100. Once the stop-off has been applied to therelevant internal sections of the first skin 116 and the second skin118, temperatures of over 900° C. and pressure are applied and theunmasked areas are bonded by Diffusion Bonding. In the example shown inFIG. 4, the first set of alternating longitudinal sections 122 of thewall 120 are bonded to the second skin 118 and the second set ofalternating longitudinal sections 124 of the wall 120 are bonded to thefirst skin 116. The sections of the first skin 116 and the second skin118 to which the stop-off 130 is applied are not bonded to the wall 120.This technique provides broad freedom for an operator to producegeometry of the heat exchanger 100 to suit the design. The diffusionbonded “flat-pack” so produced is assembled in a Superplastic Formingtool and with a means of introducing argon gas for the purposes ofinflating the structure so as to cause the skin sheets to form outwardsinto an internal die mould tool and in so doing cause the internal walls120 to be stretched from their initial horizontal planar aspect intoinclined angular walls 120. The holes 142 that are subsequently to beused for the transfer of fluid between the channels may conveniently beused to facilitate the transfer of forming gas across the heat exchangerduring the SPF part of the manufacturing process. The pressurisedforming gas itself may be introduced through the same ports as willsubsequently be used for the entry and exit of the heat exchanger media.

The SPF/DB process enables the production of thin-walled but rigiddesigns. The process is governed by specifically developedSPF-parameters and an advanced tooling concept in which the thickness ofthe panel is controlled as required. This method conforms to the bestreplication of the actual environment to which the heat exchanger 100would be exposed.

A test has been conducted to determine the heat transfer by the heatexchanger 100. A John Shaw 600 Tonne press may be arranged with a firstplaten and second platen areas with a fixed base and a moving upper“slide” operated from a central singular double-acting hydrauliccylinder able to open and close the press and apply a closure force ofup to 600 Tonnes. In one example, the first platen and the second platenis made up of five individual segments running left to right and witheach segment further sub-divided into three zones front to rear.

Hence, in this example, each platen (first and second platens) comprises15-off individual temperature control zones (30 in total). In thisexample the platen area is 1950×1450 mm with an effective heated area of1750×1250 mm, where temperature is controlled to within ±3° C. Theheater power is nominally set at 4.5 W/cm² per platen surface. Theplatens are heated by embedded electric cartridge elements with eachzone controlled via a pair of thermocouples also embedded within eachzone of the platen body. The press displays the set point temperatureand actual temperature of each individual platen zone together with thepercentage of maximum power being input to each zone.

The press has three independent argon gas pressure lines. Gas pressuresof up to ˜650 psi (45 Bar) may be applied on each gas line using Tescomgas control valves. Each gas line has a gas flow meter to record flow,as well as pressure monitoring gauges. The SPF-DB tooling is maintainedin a closed position using tonnage that is modulated based on thepressure applied and the plan view area that the gas pressure is appliedover together with an over-arching “seal force” that maintains aprogrammable net closure force regardless of pressure. The “hot zone” ofthe press is closed via vertically moving front and rear access doorsand non-moving side panels that provide a blast-proof working zonecapable of withstanding an un-contained rupture of the component.However, unanticipated movement of the upper slide structure due toinadequate hydraulic force would also provide automatic cycle abort tovent the working pressure.

A description of the testing of the heat exchanger 100 is describedbelow. The test was conducted by:

-   -   Using the Superplastic Forming—Diffusion Bonding press to hold        the first platen 116 of the heat exchanger 100 at a constant        temperature representative of an actively cooled aircraft skin        surface in a normal operation at the hypersonic flight        condition.    -   Pass the coolant fluid into the heat exchanger 100 and measure        the level of thermal energy extracted from the heat exchanger        100 into the coolant flow, which will be measured based on the        temperature difference of the coolant fluid between the inlet        port 112 and outlet port 113.

During the initial phase of the experiment the coolant gas wasincrementally increased to the following flow rates: 100, 200 & 440Standard Litres Per Minute. In order to maintain the desired pressure inthe system it was necessary to increase the demanded pressure from theArgon farm from 20 bar (300 psi) to 24 bar (350 psi). At each of theflow rates it was necessary to adjust the throttle valve to balance theflow and pressure in the system. The first platen 116 may be subject toa temperature of approximately 350 degrees Celsius in use.

Heaters were used to simulate temperatures that the first skin 116 andthe second skin 118 may experience in use. The test was to expose theheat exchanger 100 to a representative environment of a hypersonicflight envelope (thermodynamic only) as indicated below. Note that eachnumber in the table represents a corresponding plan view area of thefirst platen and the second platen respectively.

First Platen:

230 250 350 250 230 230 250 350 250 230 230 250 350 250 230

Second Platen:

210 210 190 210 210 210 210 235 210 210 210 210 235 210 210

Test runs of at least 30 minutes were completed at the nominal condition(440 Standard Litres Per Minute, 20 barg, approximately 190° C. inlettemperature for the coolant fluid entering the inlet ports 112), and thetwo flow rate variations of 420 Standard Litres Per Minute and 400Standard Litres Per Minute (SLPM).

Inlet Flow Rate Pressure Temperature (Range)/ (Range)/ Parameter(Range)/° C. SLPM barg Nominal 190 (18.7, ±5%) 440 (44, ±5%) 20.0 (2.0,±5%) 440 SLPM 182.7 (0.7) 440.2 (1.9) 19.37 (0.18) Run 1 440 SLPM 183.0(0.9) 440.2 (1.2) 19.29 (0.15) Run 2

In this test example, the coolant fluid was Argon gas. At 440 SLPM therewas a temperature increase of the coolant fluid between the inlet port112 and the outlet port 113 of just less than 100° C., whichdemonstrates that the tested heat exchanger 100 is capable of drawingthermal energy imparted by press platen into the coolant fluid whilemaintaining an acceptable temperature of the structure of the heatexchanger. The coolant fluid outlet temperature is approximately 280° C.

Utilising the gas temperature and pressure it is possible to determinethe thermodynamic and transfer properties of the coolant fluid, inparticular the specific heat at constant pressure (Cp), with which whencombined with the mass flow rate (i) and change in gas temperatureacross the test article (ΔT) it is possible to calculate the heattransferred into the gas (Q). In both cases for 440 SLPM there wasapproximately 0.49 kW transferred into the gas stream.

Q=m′CpΔT

The test was run again at 420 SLPM. The runs were conducted as follows:

Flow Rate Pressure Temperature (Range)/ (Range)/ Parameter (Range)/° C.SLPM barg Nominal 190 (18.7, ±5%) 420 (42, ±5%) 20 (2, ±5%) 420 SLPM184.8 (0.8) 420 (1.9) 19.37 (0.19) Run 1 420 SLPM 185.0 (0.4) 420 (2.2)19.27 (0.19) Run 2

At 420 SLPM there was a temperature increase of the coolant fluidbetween the inlet port 112 and the outlet port 113 of just under 100°C., and approximately 1° C. less than at 440 SLPM. This clearlydemonstrates that the heat exchanger 100 is capable of drawing thermalenergy imparted by press platen into the gas stream while exhibiting asmall difference to the 440 SLPM runs.

Utilising the gas temperature and pressure it is possible to determinethe thermodynamic and transfer properties of the Argon gas. With whichwhen combined with the flow rate and change in gas temperature acrossthe test article it is possible to calculate the heat transferred intothe gas. In both cases for 420 SLPM there was approximately 0.46 kWtransferred into the gas stream. This is approximately 0.03 kW less thanat 440 SLPM.

The test was run again at 400 SLPM. The runs were conducted as follows:

Flow Rate Pressure Temperature (Range)/ (Range)/ Parameter (Range)/° C.SLPM barg Nominal 190 (18.7, ±5%) 400 (40, ±5%) 20 (2, ±5%) 400 SLPM187.0 (0.8) 400 (1.9) 19.34 (0.14) Run 1 400 SLPM 187.3 (0.4) 400 (1.4)19.4 (0.18) Run 2

At 400 SLPM there was a temperature increase of the coolant fluidbetween the inlet port 112 and the outlet port 113 of just less than100° C., and approximately a further 1° C. less than at 420 SLPM. Thisclearly demonstrates that the heat exchanger was capable of drawingthermal energy imparted by press platen into the gas stream whileexhibiting a small difference to the 420 SLPM runs. Additionally thissupports the trend of a reduction of 20 SLPM resulting in a 1° C.decrease in the gas temperature difference across the heat exchanger.

Utilising the gas temperature and pressure it is possible to determinethe thermodynamic and transfer properties of the coolant fluid. Withwhich when combined with the flow rate and change in gas temperatureacross the test article it is possible to calculate the heat transferredinto the gas. In both cases for 400 SLPM there was approximately 0.43 kWtransferred into the gas stream. This is approximately 0.03 kW less thanat 420 SLPM and approximately 0.06 kW less than at 440 SLPM.

Based on the initial calculations of the heat transfer into the gas flowa linear relationship to the mass flow is evident.

The table below is a Summary of Heat Transfer Calculated for VariousFlow Rates:

Approximate Heat Transfer Flow/SLPM Mass Flow/kg/s to Gas Flow/W 4400.01208 490 420 0.01153 460 400 0.01098 430

FIG. 9 shows an example of the relationship between heat transfer andmass flow rate. As can be seen from FIG. 9, the heat transfer to thecoolant fluid follows a linear relationship dependent upon mass flow.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

What is claimed is:
 1. A heat exchanger comprising: at least one set ofchannels having a proximal end and a distal end, the set of channelscomprising: a first channel defined by a first skin and a wall; and asecond channel defined by a second skin and the wall, wherein the walllocated between the first channel and the second channel comprises afirst at least one aperture to allow fluid to pass through the wall fromthe first channel to the second channel.
 2. The heat exchanger accordingto claim 1, wherein the heat exchanger comprises an inlet port forreceiving said fluid and an outlet port for allowing the fluid to exitthe heat exchanger.
 3. The heat exchanger according to claim 2, whereinthe inlet port is coupled to the first channel and the outlet port iscoupled to the second channel.
 4. The heat exchanger according to claim3, wherein the inlet port and the outlet port are arranged at theproximal end of the set of channels.
 5. The heat exchanger according toclaim 3, wherein the inlet port is arranged at the proximal end of theset of channels and the outlet port is arranged at the distal end of theset of channels.
 6. The heat exchanger according to claim 2, wherein theset of channels comprises a third channel defined by the first skin andthe wall, wherein the wall located between the second channel and thethird channel comprises a second at least one aperture to allow fluid topass through the wall from the second channel to the third channel. 7.The heat exchanger according to claim 6, wherein the inlet port isconnected to the first channel at the proximal end of the set ofchannels and the outlet port is connected to the third channel at thedistal end of the set of channels.
 8. The heat exchanger according toclaim 7, wherein the second at least one aperture is located towards theproximal end of the set of channels.
 9. The heat exchanger according toclaim 1, wherein the first at least one aperture is towards the distalend of the set of channels.
 10. The heat exchanger according to claim 1,wherein the set of channels follow a non-linear path between theproximal end and the distal end.
 11. The heat exchanger according toclaim 10, wherein the first channel and the second channel are parallelcurves relative to each other.
 12. The heat exchanger according to claim10, wherein the non-linear path is substantially sinusoidal.
 13. Theheat exchanger according to claim 1, wherein the wall is bonded to thefirst skin and the second skin.
 14. The heat exchanger according toclaim 13, wherein the wall is corrugated and comprises a firstlongitudinal section bonded to the first skin, a second longitudinalsection bonded to the second skin and at least one inclined sectionbetween the first longitudinal section and the second longitudinalsection.
 15. The heat exchanger according to claim 14, wherein theinclined section is inclined at an angle of approximately 30 to 60degrees relative to the first longitudinal section and the secondlongitudinal section.
 16. The heat exchanger according to claim 1,wherein the wall has a thickness of between 0.5 mm and 6 mm.
 17. Theheat exchanger according to claim 1, wherein the first skin and thesecond skin are formed of a titanium alloy.
 18. The heat exchangeraccording to claim 1 further comprising a plurality of sets of channels.19. The method of manufacturing a heat exchanger as described in claim1, wherein the heat exchanger is manufactured using diffusion bondingand superplastic forming.